The wide band oxygen sensor is the ultimate addition to any new or existing Commander 950 EFI system. It will plug directly into any Commander 950 harness and accurately measure any air/fuel ratio between 10:1 and 18:1. This allows the engine tuner to read the air/fuel ratio in real time for extremely accurate tuning. The 534-197 upgrade kit is intended for the cost conscious consumer who wants the tuneability of a wide band oxygen sensor but cannot afford the high prices generally associated with a wide band oxygen sensor. The 534-197 can also be upgraded later for use with a NTK sensor by simply reconnecting a jumper loop and purchasing the NTK sensor. This upgrade kit requires you to have the "PRO" C950 software and firmware. Commanders 950 ECU's manufactured in 2004 and later already have "Pro firmware installed. So your ECU is older than 2003? No need to worry the kit also includes a certificate that allows the ECU to be returned to Holley for a free "PRO" firmware upgrade. Also, the "PRO" software and manual are available for downloading at http://www.holley.com/TechService/Library.asp.